A wiper blade for wiping a surface of a windshield has a wiper rubber and a lever assembly. The wiper rubber contacts the windshield surface. The lever assembly holds and supports the wiper rubber along its longitudinal direction. The lever assembly of a conventional wiper blade includes one main lever and a plurality of yoke levers linked to the main lever. The main lever is connected to the wiper arm. The yoke lever is linked to the main lever or another yoke lever at its middle. The main lever and the yoke lever are hinge-connected by means of a pin or rivet which passes through the main lever and the yoke lever.
When a motor vehicle runs, wind or air stream impinging against the windshield applies a force to the wiper blade throughout the longitudinal direction of the wiper blade. The force caused by the wind or air stream acts to lift the wiper blade from the windshield surface. The faster the motor vehicle runs, the stronger such a lift force becomes. This weakens the contact between the wiper rubber and the windshield surface, thereby deteriorating wiping performance.
To address the deterioration in wiping performance caused by the lift of a wiper blade, it is known in the art to attach a spoiler to the wiper blade. The spoiler interacts with wind or air stream and thereby applies a force in a direction opposite to the lift of the wiper blade. By way of example, Korean Patent Application Publication No. 2001-0030699 proposes a wiper blade with a spoiler attached to a main lever. It is also known in the art to attach a cover, which covers the main lever or the yoke lever of the wiper blade and has the shape of a spoiler, to the wiper blade. By way of another example, Korean Patent Application Publication No. 2006-0051763 proposes a wiper blade with such a cover.